In order to ensure the microbiological safety of foods and clinical environments it is often necessary to sample the surfaces of carcasses, or food manufacturing equipment, or other surfaces, to determine the existence and quantity of microorganisms, or other analytes, such as adenosine triphosphate, thereon. It is usually impractical to measure either microorganisms or hygiene-pertinent analytes directly at a surface because they are very small analytical quantities. Therefore, it is a common practice to remove them from the surface in some way and disperse them in water or other liquid so that they can be measured at a laboratory, for example, by culturing suspended microorganisms. Microorganisms may exist on surfaces in a variety of states. They may be loosely attached to surfaces, in which case they are easily removed; alternatively, they may be adsorbed on the surface or attached in biofilms or trapped in pores, in which case considerably greater effort if required to disperse them. This variability causes problems of reproducibility because usually it is not possible to maintain the suspending liquid and surface in contact with each other long enough to reach an equilibrium.
Many techniques and devices have been developed or proposed with the aim of obtaining representative suspensions of the microorganisms at surfaces, for example, swabbing the surface, shaking the test sample with liquid in a plastic bag, using a liquid spray gun in a sealed container, or by excising a portion of the surface and blending it in a liquid in a blender or other device which disrupts and disperses the microorganisms.
U.S. Pat. No. 4,281,066 to V. Thran, et al, discloses all apparatus for taking samples from surfaces that includes a nozzle for spraying a rinsing liquid atomized by a compressed gas onto the test surface and a container for collecting rinsed-off particles and rinsing liquid. This apparatus requires a compressor and a relatively large quantity of liquid for a small sample area. Also with the arrangement of collector vessel as shown, use is limited to vertical or near vertical surfaces.
None of the prior techniques are entirely satisfactory for a variety of reasons. For example, swabbing is convenient and does not harm the test surface, but is imprecise in its yield of microorganisms; shaking the test sample in a plastic bag is practicable only for small test samples such as chickens; neither shaking nor rinsing with liquid are energetic enough to remove most of the microorganisms; spray techniques are difficult to use when the test sample surface is at angles inclined from the horizontal; and techniques requiring excision destroy the surface and reduce the value of the sample.
There is a need for an analyte suspending device that is simple and inexpensive to operate, non-destructive to the object being tested, that removes a high proportion of bacteria or other analyte from the test surface into liquid suspension, and that call be used on surfaces at any orientation.